Myositis ossificans occupying the thenar region: a case report

Abstract

IntroductionMyositis ossificans is a benign, self-limiting, tumor-like lesion that usually affects the elbow and thigh; occurrence in the hand is uncommon. We report a rare case of a patient with myositis ossificans in the thenar region.Case presentationA 15-year-old Japanese girl presented to our hospital with a 2-month history of a painful mass in the right thenar region without previous trauma. The clinical and radiological examination findings suggested an osteoblastic malignancy. A diagnosis of myositis ossificans was made on the basis of an incisional biopsy. Despite the location of the lesion in the thenar region, a normal functional outcome was achieved after marginal resection of the mature lesion.ConclusionsClinicians should consider myositis ossificans as a possible diagnosis for a soft tissue mass in the hand, thereby avoiding unnecessarily aggressive therapy.

A sporadic case of myositis ossificans of the forearm presenting clinically as mesenchimal tumor

“…Clinical presentation of myositis ossificans is generally characterized by an ossifying soft-tissue mass. It can present incidentally, as in our patient, or acutely with pain, limitation of joint movement, or complications arising from nerve compression 1,6 . Early in the disease, the affected area is soft, swollen and painful.…”

“…Within six weeks, a firm and often painful mass develops in the affected muscles. This lesion matures over 6-12 months, and eventually ossifies and becomes hard, painless and well-circumscribed 1,2,6,7,12,14 . As a result, patients report muscle pain that persists longer than would be expected for a simple muscle strain or contusion.…”

“…The histologic course of myositis ossificans progresses from an immature highly cellular fibroblastic lesion to a mature mass with peripheral lamellar bone 1,12,14 . With maturation of the lesion, a typical zonal pattern develops with three distinct zones: the centre zone consisting of rapidly proliferating stromal fibroblasts with areas of haemorrhage and necrotic muscles; the intermediate zone characterized by osteoblasts with immature osteoid formation; and the peripheral zone composed of mature lamellar bone separated from the surrounding tissue by fibrous and muscle tissue 1,3,4,6,9,12 . All of these pathohistological characteristics that are typical for myositis ossificans had also our patient in pathohistological examination of the specimen.…”

“…To our knowledge, the youngest documented patient was a five-monthold girl 13 and the oldest an 83-year-old woman 14 . Generally, the most affected areas in the upper extremity are the flexor muscles, particulary the brachial muscle, as well as the quadriceps, hamstrings, and gluteus muscles in the lower extremity 4,6,12 . However, involvement of the forearm is very rare and only few cases have been reported so far.…”

“…This condition is characterized by focal formation of heterotopic bone and cartilage in extraskeletal soft-tissue [1][2][3] . Most commonly affected areas are the flexor muscles of the arm and the extensor muscles of the thigh [4][5][6] . Myositis ossificans has a prevalence of less than 1 per 1 million, and it usually occurs in active adolesmyositis ossificans occuring in the right forearm that presenting clinically as mesenchimal tumor mass suspicious for malignant fibrous histiocytoma tumor.…”